\documentclass{article}
\usepackage{pgfplots}

\pgfplotsset{compat=1.11}

\begin{document}
\begin{tikzpicture}
%\tracingcommands=2 \tracingmacros=2
	\begin{axis}[grid=major]
	\addplot+[
		unbounded coords=jump,
		x filter/.expression={x+1},
		y filter/.expression={(abs(x) < 0.5) ? nan : y},
	]
	{x+1};
	\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
	\begin{axis}[grid=major]
	\addplot+[
		unbounded coords=jump,
		x filter/.expression={x+1},
		y filter/.expression={y==3 ? nan : y},
	]
	table {
	x y 
	1 2
	1.5 2.5
	2 3
	2.5 3.5
	3 4
	};
	\end{axis}
\end{tikzpicture}

\end{document}
